Evaluation of persistent organochlorine pesticides and polychlorinated biphenyls in Umgeni River bank soil, KwaZuluNatal, South Africa

is study investigated the presence and distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in soil collected along the banks of the Umgeni River, one of the largest rivers in the province of KwaZulu-Natal, South Africa. e analysis was performed using gas chromatography-mass spectrometry (GC-MS). e results showed that the levels of OCPs ranged from 3.58±0.09 ng/g for hexachlorobenzene (HCB) to 82.65±2.82 ng/g for HCH, with an individual mean concentration of 24.33±2.00 ng/g dry weight (dw). e levels of PCBs ranged from 10.46 ng/g for PCB105 to 89.46 ng/g for PCB180, with an average PCB value of 25.47±1.26 ng/g, dw. e highest levels of OCPs and PCBs were found at Northern Wastewater Treatment Plant (mean OCP: 32.39±3.97 ng/g and PCB: 67.87±1.67 ng/g). e two most abundant contaminants in the river were endrin and PCB180.Keywords: Umgeni River, bank soil, OCPs, PCBs, gas chromatography mass spectrometr

Use of bipolar electrochemistry in nanoscience: contact free methods for the site selective modification of nanostructured carbon materials (The)

Bipolar electrochemistry occurs when an isolated conductive substrate inside an electric field supports both oxidation and reduction reactions. The method requires no direct contact between the power supply and the substrate. In the following thesis bipolar electrochemistry has been used to deposit palladium onto isolated graphite platelets, carbon nanofibers (CNF), and carbon nanotubes (CNT), as well as, various metals, a semiconductor, and an electropolymer on CNTs. Initial work used pulsed DC electric fields to deposit palladium onto isolated graphite platelets. Transmission electronmicroscopy (TEM) studies on the platelets found palladium metal on one area, indicative of a bipolar mechanism, and palladium deposits that varied from surface bound to highly ramified deposits. No correlation was found betweenthe frequency used to prepare the deposits and the palladium metal dispersion. The same field intensities and frequencies used on the graphiteplatelets were used to produce CNFs with palladium on one tip. The amount of palladium deposited on one tip of a CNF was controlled by adjusting how long the electric field was applied. Preliminary experiments to produce bulkquantities of CNFs with palladium bipolar electrodeposits used CNFs ball milled with silica, and CNFs suspended in tetrahydrofuran or methylene chloride. The palladium content, measured by atomic absorption spectroscopy,of the functionalized CNFs in silica showed no difference with increased CNF loading; however, TEM studies found a small number of functionalized CNFs with palladium on one tip. Work on CNFs suspended in THF and methylenechloride used suspensions with high loadings of CNFs which led to small percentages of CNFs with bipolar electrodeposited palladium. Finally CNTsobtained commercially and CNTs grown using chemical vapor deposition were successfully functionalized using bipolar electrodeposition. These experiments demonstrate a reliable and controlled method to modify nanostructured materials.Ph.D., Chemistry -- Drexel University, 200

Semi-empirical supported, Ab initio derived thermodynamic properties for ClO2 and its sub and extended species, applied in water treatment cycles

DATA AVAILABILITY : The data used to support the findings of this study are included in the article and within the supplementary information file.Please read abstract in the article.The Faculty of Natural and Agricultural Sciences, at the University of Pretoria.http://www.cell.com/heliyonhj2024Centre for the Advancement of ScholarshipChemistrySDG-06:Clean water and sanitatio

Rainfall and Temperature Trends and Variability in Arid and Semi-arid Lands of Kitui County, Kenya

A study was carried out to analyse rainfall and temperature trends and variability in selected agro-ecological zones in Kitui County. Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) rainfall dataset was used while temperature data was obtained from the Climatic Research Unit gridded Time Series (CRU TS) dataset. The results indicated that there was a non-significant decreasing trend (p<0.05) in average annual rainfall in all the four agro-ecological zones (p<0.05) for a 30-years period (1988-2018) in the study area. A decreasing trend in March-April-May (MAM) seasonal rainfall trend was reported in the arid and semi-arid agro-ecological zones while an increasing trend was recorded in the transitional and semi-humid zones. For the October-November-December (OND) seasonal rainfall, a non-significant decreasing trend was reported in all the four agro-ecological zones. Additionally, a higher annual rainfall variability was recorded in the drier (arid) and wetter (semi-humid) zones compared to that in semi-arid and transitional zones. Moreover, the study established that there was a spatial variation in both MAM and OND seasonal rainfall variability and that rainfall variability was higher in the OND seasonal rainfall than that of the MAM seasonal rainfall in all the agro-ecological zones. With reference to temperature trends, a statistically significant increasing trend in annual and OND seasonal average maximum and minimum temperatures was reported in all the four agro-ecological zones. Further, the study noted a non-significant increasing trend in maximum and minimum temperatures for the MAM season in all the agro-ecological zones. In regard to temperature variability, the study deduced that there was low temperature variability compared to rainfall variability in all the four agro-ecological zones. The study recommends that location-specific rainfall and temperature analysis should guide planning and implementation of adaptation strategies for effective response to climate variability. Keywords: Agro-ecological Zones, Mann-Kendall Test, Coefficient of Variation, CHIRPS, CRU TS DOI: 10.7176/JEES/12-12-05 Publication date: December 31st 202

Chemical, mineralogical and morphological investigation of coal fly ash obtained from Mpumalanga Province, South Africa

Abstract: Background and Objective: Coal fly ash generated from the combustion of coal by thermal power plant stations are enormous and the disposal there of is a big problem. In the present study, the chemical, mineralogical and morphological characterization of coal fly ash samples (CFAs) obtained from Mpumalanga province, South Africa were investigated. Materials and Methods: The CFAs were characterised by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), high resolution transmission electron spectroscopy (HRTEM) and the selected area electron diffraction (SAED) analytical technique. Result: Experimental results showed that the CFAs contain hematite, magnetite, calcite, lime, mullite and quartz. The CFAs are polycrystalline, could be categorized as class F fly ash and the particles are spherical in shape. Conclusion: The phase characterization suggested that CFA could be used for the synthesis of nanoparticles, as well as extraction of valuable metals, more so, the elemental composition of the CFAs suggested that the storage and disposal of CFAs could lead to the release of salts and toxic elements into the environment, thereby, contaminating surface and ground waters

Low temperature synthesis of multiwalled carbon nanotubes and incorporation into an organic solar cell

Abstract: Metal nanoparticle (MNP) catalysts used for the synthesis of multiwalled carbon nanotubes (MWCNTs) consisted of single metals (Fe, Ni or Co) and bimetallic mixture (CoFe, NiFe or NiCo). MWCNTs were successfully synthesised at 200 _C in 10 min using liquefied petroleum gas as carbon source with non-equilibrium plasma enhanced chemical vapour deposition (PECVD) method. The nanostructures and the morphology of the MNPs and the MWCNTs film were characterised using relevant microscopic and spectroscopic methods. The synthesised MWCNTs were used as part of the electrode material in organic solar cell (OSC) set-up. Poly (3,4- ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) was used as an electron transporter and poly-3-hexyl thiophene (P3HT) as an electron donor. The performance of OSC devices was tested using standard electrical measurements and solar simulator operating at 100 mW/cm2. The measured power conversion efficiencies was found to be dependent on the metal catalyst used during synthesis. Among all the catalysts employed in this investigation, the best device performance was found from the synthesis of MWCNTs using Fe as a catalyst followed by Co and then Ni, respectively

Exploration of the different dimensions of wurtzite ZnO structure nanomaterials as gas sensors at room temperature

DATA AVAILABILITY : Data is available when request made.SUPPLEMENTARY MATERIALS : FIGURE S1: Sensors performance measurement setup; FIGURE S2: FTIR spectra of the (a) synthesized ZnO nanostructures, i.e., nanoflowers (N.F.), nanosheets (N.S.), nanorods (N.R.), and nanoparticles (N.P.); (b) candle soot, and (c) purchased cellulose acetate respectively; FIGURE S3: BET isotherm; FIGURE S4: UV-vis diffuse reflectance spectra and bandgap energy values of the (a) synthesized ZnO nanostructures, i.e., nanoflowers (N.F.), nanosheets (N.S.), nanorods (N.R.), and nanoparticles (N.P.); (b) candle soot, and (c) purchased cellulose acetate; FIGURE S5. Dynamic response and recovery curves 3:1:1 mass ratio towards ethanol vapor (a) nanoparticles and (b) calibration curve; (c) nanorod and (d) its calibration curve; (e) nanoflower (f) its calibration curve; FIGURE S6. Dynamic response and recovery curves 2:1:1 mass ratio towards ethanol vapor (g) nanorod and (h) calibration curve; (i) nanosheet and (j) its calibration curve; (k) nanoflower (l) its calibration curve; FIGURE S7: Dynamic response and recovery curves 1:1:1 mass ratio of towards isopropanol vapor (a) nanorod and (b) calibration curve; (c) nanosheet and (d) its calibration curve; (e) nanoflower (f) its calibration curve; FIGURE S8: Static response and recovery curves 1:1:1 mass ratio of towards methanol; TABLE S1: Band gap energy (Eg), Average crystallite size (d) and surface area (A) of nanostructured oxides; TABLE S2: Summary of the performance of the fabricated sensors when detecting ethanol vapour; TABLE S3: Summary of the performance of the fabricated sensors when detecting isopropanol vapor [67–72].Please read abstract in the article.The National Research Foundation of South Africa and the Centre for Nanomaterials Sciences Research, University of Johannesburg, South Africa.https://www.mdpi.com/journal/nanomaterialsam2024ChemistryNon

Design of multi-layer graphene membrane with descending pore size for 100% water desalination by simulation using ReaxFF

DATA AVAILABILITY STATMENT : Data are available upon request from the corresponding author and based on university rules.The performance of a desalination membrane depends on a specific pore size suitable for both water permeability and salt rejection. To increase membrane permeability, the applied pressure should be increased, which creates the need to improve membrane stability. In this research article, a molecular dynamics (MD) simulation was performed using ReaxFF module from Amsterdam Modeling suite (AMS) software to simulate water desalination efficiency using a single and multi-layer graphene membrane. The graphene membrane with different pore sizes and a multi-layer graphene membrane with descending pore size in each layer were designed and studied under different pressures. The stability of the membrane was checked using Material Studio 2019 by studying the dynamics summary. The single-layer graphene membrane was evaluated under pressures ranging from 100 to 500 MPa, with the salt rejection ranging from 95% to 82% with a water permeability of 0.347 109 to 2.94 109 (mm.g.cm2s1.bar1), respectively. Almost 100% salt rejection was achieved for the multi-layer graphene membrane. This study successfully demonstrated the design and optimization of graphene membrane performance without functionalization.The Faculty of Sciences at the University of Johannesburg, South Africa,https://www.mdpi.com/journal/membranesam2023Chemistr